From mboxrd@z Thu Jan  1 00:00:00 1970
From: Pat LaVarre <p.lavarre@ieee.org>
Subject: Re: [usb-storage] Re: iRiver H100 series and usb-storage issues
Date: 08 Jun 2004 10:10:05 -0600
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To: James Bottomley <James.Bottomley@SteelEye.com>
Cc: linux-scsi@vger.kernel.org, usb-storage@lists.one-eyed-alien.net, Alan Stern <stern@rowland.harvard.edu>, Philippe Troin <phil@fifi.org>

James B:

> underflow ... meaning ... supposed to be
> "return an error if you transfer fewer than underflow bytes".
> The error's not specified,
> but something like DID_ERROR with SUGGEST_RETRY should be fine.

Incisive, thank you.

> ... Usually HBAs ignore underflow,
> because it simply works correctly ...

Is there an easy way to test whether an HBA implements underflow
correctly?

For example, to inject an underflow into ioctl SG_IO, trivially I ask
for a one block read CDB to fill a two block buffer.

Pat LaVarre

P.S. A possibly relevant glance into the source is:

http://lxr.linux.no/search?v=2.6.5&string=underflow
search: SCSI
http://lxr.linux.no/source/drivers/scsi/sd.c?v=2.6.5#L374
...
static int sd_init_command(struct scsi_cmnd * SCpnt)
...
SCpnt->underflow = this_count << 9;
...